The Midland Main Line is a major railway line in England from London to Sheffield in the North of England. The line is under the Network Rail description of Route 19; it comprises the lines from London's St. Pancras station via Leicester, Derby/Nottingham and Chesterfield in the East Midlands.
Express passenger services on the line are operated by East Midlands Trains. The section between St Pancras and Bedford is electrified and forms the northern half of Thameslink (mainly operated by Thameslink and Great Northern), with a fast service to Brighton and other suburban services.
A northern part of the route, between Derby and Chesterfield, also forms part of the Cross Country Route operated by CrossCountry. Tracks from Nottingham to Leeds via Barnsley and Sheffield are shared with Northern. East Midlands Local also operates regional and local services using parts of the line.
The Midland Main Line was built in stages between the 1830s and the 1870s. The earliest section was opened by the Midland Counties Railway between Nottingham and Derby on 4 June 1839. On 5 May 1840 the section of the route from Trent Junction to Leicester was opened.